Capacity control means for rotary compressors



R. B. TOSH June 24, 1969 CAPACITY CONTROL MEANS FOR ROTARY COMPRESSORS IFiled June 14. 1967 Sheet INVENTOR ROY B. TOSH ATTORNEY June 24, 1969 R.B. T-OSH 3,451,614

CAPACITY CONTROL MEANS FOR ROTARY COMPRESSORS Filed June 14, 1967 Shet 2of 4 INVENTOR.

ROY B, TOSH June 24, 1969 R B. TOSH 3, 5

CAPACITY CONTROL MEANS FOR ROTARY COMPRESSORS Filed June 14, 1967 Sheetof 4 l-Tlllll mmvrolc ROY B. TOSH AT TORNE Y June 24, 1969 'R.B.TOSH3,451,614

CAPACITY CONTROL MEANS FOR ROTARY COMPRESSOR S Filed Jfine 14, 1967Sheet 4 of 4 mvz-smom ROY B. TOSH ATTORNfY United States Patent U.S. Cl.230138 2 Claims ABSTRACT OF THE DISCLOSURE The capacity control devicefor a rotary compressor of the sliding vane type comprises a bypass portmeans, including a bypass conduit, in an end wall of the compressor andconstructed and arranged to communicate with the fluid compressionpockets formed between next adjacent vanes prior to substantialcompression of the fluid trapped in such pockets and to pass the fluidfrom the pocket into the bypass conduit which is in communication withthe compressor suction or inlet port. The device also includes a valvemeans consisting of an arcuate plate disposed to overlie the bypass portmeans and supported for rotation relative to the bypass port means tovary the area at the bypass port means and the fluid flow therethrough.The areuate plate is connected to an actuating means which, in turn, isconnected to a source of rotary power for effecting rotation thereof inresponse to the demand requirements on the compressor.

This invention relates to compressors and, more particularly, to rotarycompressors and means for controlling the capacity of such compressorsin accordance with the demand thereon.

In rotary compressors of the type comprising a barrel or housing and arotor, carrying circumferentially spaced, sliding vanes, eccentricallysupported for rotation in the barrel (hereinafter simply referred to asa rotary compressor), it has been common practice to provide a bypassmeans, including valve means, for communicating the compressor dischargeoutlet port with the suction or inlet port of the compressor to therebyrecirculate all or a portion of the discharged fluid back to the inletof the compressor in accordance with the load or demand on thecompressor. This means of compressor capacity control is inefiicientbecause the compressor is always extending the same amount of energy tocompress the entire fluid capacity regardless of the demand. In otherwords, the compressor in less than full capacity operation isunnecessarily fully recompressing the bypassed fluid.

Another known compressor capacity control means is one which comprisesplurality of spaced unloading or dumping valves, one or more of which isopen for less than full capacity operation. In view of structurallimitations, the number of such valves is limited so that it is notpossible to obtain very accurate capacity adjustment in relation to thedemand.

Accordingly, it is one of the objects of the present invention toprovide an improved capacity control means for a rotary compressor,which means is more efficient, in that it effects a conservation of thepower to drive the compressor, than heretofore known capacity controldevices.

It is another object of this invention to provide an improved capacitycontrol means for a rotary compressor, which means is capable ofinfinite steps of adjustment of capacity.

It is a further object of the present invention to provide an improvedcapacity control means which is relatively inexpensive to manufacture,low in maintenance cost and desirable from the standpoint of resultsobtained and cost of operation.

In view of the foregoing, the present invention contemplates an improvedcapacity control means for a. rotary compressor, which means comprises abypass port means formed in an end wall of the compressor housing incommunication with the compression pockets or working chambers formedbetween next adjacent vanes before substantial compression of the fluidtrapped therein and a bypass conduit which communicates with thecompressor inlet port. Also, a valve means is disposed adjacent the.bypass port means and supported for slidable arcuate movement relativeto the bypass port means to control flow of fluid, through the bypassport means, into the bypass conduit. An actuating means is constructedand arranged to engage said valve means to arcuately move the latter inresponse to compressor demand.

The invention will be more fully understood from the followingdescription thereof when considered in connection with accompanyingdrawings in which:

FIG. 1 is a view partly in cross-section and partly in elevation of arotary compressor having a capacity control means according to thepresent invention;

FIG. 2 is a transverse cross-sectional view taken substantially alongline 22 of FIG. 1, looking in the direction of the arrows, showing thefully open position of the capacity control means;

FIG. 3 is another operative view of the parts shown in FIG. 2 showingthe fully closed position of the capacity control means;

FIG. 4 is a transverse cross-sectional view taken substantially alongline 4-4 of FIG. 1, looking in the direction of the arrows and with thebypass port of the capacity control means shown in dash-dot lines;

FIG. 5 is a fragmentary view in section taken along line '5--5 of FIG. 2on a somewhat enlarged scale.

Now referring to the drawings and more particularly to FIG. 1, thereference number 10 generally designates a rotary compressor which isprovided with a capacity control means, generally designated 12,according to the. present invention.

The rotary compressor '10 is of the sliding vane type and may be similarin construction to that disclosed in United States Patent No. 3,291,384.While the compressor is shown and will be hereinafter described as beingof the type disclosed in the aforementioned United States patent, it isto be clearly understood that the invention is not to be construed aslimited thereto. The capacity control means 12 has application to anyrotary compressor of the sliding vane type without departing from thescope and spirit of this invention.

As shown in FIG. 1, rotary compressor 10 consists of a barrel or housing14, a rotor 16 eccentrically supported in the housing by bearings 18disposed in end walls or hearing housings 20 and 22 secured to housing14 by a plurality of bolts 23. As best shown in FIG. 4, the compressoris also provided with an inlet or suction port 24 disposed in housing 14and connected to receive fluid to be compressed and an outlet ordischarge 26 disposed in housing 14 to discharge compressed fluid. Rotor16 carries a plurality of circumferentially spaced vanes 28- which aredisposed for slidable movement within grooves 30 formed in rotor 16. Theend 32 of rotor shaft 34 is connected either directly or indirectly to asuitable source of rotary power, such as an electric motor (not shown).Upon rotation of rotor 16, the outer vane edges sweepingly engage theinner surface 36 of housing 14 while the opposite end edges slidablyabut the inner surfaces of bearing housings 20 and 22. As best shown inFIG. 4, inlet port 24 and outlet port 26 are arranged in housing 14 inrelation to the eccentricity of rotor 16 so that fluid to be compressedenters into a working chamber or compression pocket 38 formed betweennext adjacent vanes 28, by reason of the negative pressure in the pocketas the pocket expands and comes into communication with the inlet port,and is trapped therein as the trailing vane 28 passes inlet port 24, thetrapped fluid being compressed upon further rotation of rotor 16 anddischarged from the pocket into the outlet port 26 when the pocket comesinto communication with the latter. To assist in effecting a seal at thevane edges, lubricate and assist in cooling the compressor, a lubricantis injected into the housing through the nozzle 39. An oil pump 41 isconnected to the rotor shaft 34 to effect circulation of lubricant tovarious parts of the compressor, including nozzle 39.

Obviously, the compressor herein described must be provided with somedevice for regulating its capacity in relation to demand or load changeson the compressor. Since it is more economical to control compressorcapacity by unloading the Working chambers thereof rather than by meansfor effecting changes in the r.p.m. of the compressor, compressor 10 isprovided with capacity control means 12, which according to the presentinvention functions to unload the working chambers or compressionpockets 38.

The capacity control means 12 comprises a bypass port 40 formed inbearing housing 22 so as to communicate with the compression pockets 38after the trailing vane has sealed pocket 38 but before substantialcompression of the fluid trapped in the pocket. In other words, thebypass port 40 is so located that the trapped fluid is compressedsufficiently to provide a pressure differential relative to the fluidpressure in inlet port 24 to cause fluid flow to the latter, but beforeunnecessary compression of the fluid to be bypassed. The bypass port 40includes a bypass passage 42 which is also formed in bearing housing 22.A conduit or pipe 44 is connected at one end to hearing housing 22 tocommunicate with bypass passage 42. The opposite end of pipe 44 isconnected to communicate with inlet port 24 to deliver bypassed fluid tothe latter through a suction manifold 45.

To control flow through bypass port 40, a valve plate 46 is disposed inabutment against the inner face of bearing housing 22 to overlie bypassport 40. The valve plate 46 is a flat ring shaped member with a hubportion 48 on which is formed a ring gear 50. As best shown in FIG. theinner face of bearing housing 22 is provided with an annular recess 52of L-shape cross-sectional configuration to receive therein valve plate46. The recess 52 is so dimensioned that valve plate 46 is free torotate within the recess and a flat surface is presented to the lateraledges of vanes 28. A retaining ring 54, having an inwardly projectingflange 56, is secured to bearing housing 22 so as to hold valve plate 46for rotative movement relative to the bearing housing. The peripheralportion of valve plate 46 is recessed to receive flange 56 so that theflange and surface of valve plate 46 lie in the same plane. As shown,retaining ring 54 may be secured to the bearing housing by deforming thering into an annular notch '58 in bearing housing 22 or by any othersuitable means. The valve plate is preferably provided with two closelyspaced elongated slots '60 which move into and out of registry withbypass port 40 when valve plate 46 is rotated. While two elongated slots60 are preferred, it is contemplated that one large slot or more thantwo openings may be provided in valve plate 46 without deviating fromthe scope and spirit of the present invention.

Oscillatory movement of valve plate 46 is effected by an actuatingmeans, including a pinion gear 62, supported for rotation on a shaft 64in bearing housing 22. As best shown in FIGS. 2 and 5, pinion gear 62 isdisposed in an arcuate recess 66, formed in bearing housing 22 tointersect recess 52, and in meshing relationship with ring gear 50 ofvalve plate 46. The shaft 64 is supported within bearing housing 22 bybearings 68 and is connected to a source of rotary power (not shown)which is respon- 4 sive to demand on compressor 10. For example, thesource of rotary power could be a rectilinear hydraulic motor connectedto receive oil from the oil pump 41 and having a spring biased pistoncarrying a gear rack which is in mesh with a second pinion gear (notshown) mounted on shaft 64.

In operation of the capacity control means 12, herein disclosed,rotation of shaft 64 by any suitable source of rotary power (not shown)in response to demand on compressor 10, causes rotation of valve plate46. As shown in FIG. 2, for ease in start-up of the compressor, thevalve plate is positioned so that slots 60* are in full registry withbypass port 40, thereby fully unloading the compressor. To provide forfull capacity operation of compressor 10, valve plate 46 is rotated sothat slots 60 are completely out of registry with bypass port 40 asshown in FIG. 3. If the demand on compressor 10 decreases, valve plate46 is rotated by pinion gear 62 to bring slots 60 into registry withbypass port 40 to the extent required to bypass sufficient fluid tocause the compressor fluid output or discharge to match the demand.Obviously, the capacity control means 12 provides an infinite stepadjustment of fluid bypass to thereby accurately match compressor outputto demand in response to changes in the latter.

When valve plate 46 is rotated to bring at least a portion of a slot 60into registry with bypass port 40, the fluid escaping from pockets 38into bypass port 40 flows into passageway 42 and, thence, into bypasspipe 44. After the fluid flows through bypass pipe 44, it dischargesinto inlet or suction manifold 45, which communicates with compressorsuction port 24 (see FIG. 4). As best illustrated in FIG. 4, bypassingof fluid is achieved after some compression of all of the fluid trappedin pockets 38' but only enough compression to insure sufficient pressuredifferential between the fluid in pocket 38 and fluid pressure insuction manifold 45 to effect flow of bypassed fluid to suction manifold45.

The compressor lubricant injected into housing 14, through nozzle 39,also lubricates the surfaces between valve plate 46 and bearing housing22 and gears 50 and 62. The lubricant also serves to seal theinterstices between valve plate 46 and bearing housing 22 to preventfluid flow through slots 60 when the slots are completely out ofregister with bypass port 40* and through the portions of or all of slot60 when the valve plate is not in the fully closed position shown inFIG. 3.

It is believed readily apparent from the foregoing disclosure that animproved capacity control means has been provided for rotary compressorswhich is relatively simple and inexpensive and is capable of infiniteincrements of adjustment to accurately match compressor output ordemand. It is also a control means which effects a conservation ofcompressor drive power by bypassing fluid before such bypassed fluid issubstantially compressed.

Although but one embodiment of the invention has been illustrated anddescribed in detail, it is to be expressly understood that the inventionis not limited thereto. Various changes can be made in the arrangementof parts without departing from the spirit and scope of the invention asthe same will now be understood by those skilled in the art.

I claim:

1. A rotary compressor having means for controlling the amount of fluidbeing compressed comprising a housing having a generally cylindricalbore, a pair of end caps closing the opposite ends of said housing, avalve plate rotatably mounted on one of said end caps adjacent to saidbore, said housing having an inlet on one side and a discharge on theother side providing communication between the exterior of said housingand said bore, bearing means mounted within each of said end caps, arotor carrying a plurality of circumferentially spaced sliding vanes,said rotor being eccentrically mounted within said bore and defining agenerally crescent shaped chamber, said sliding vanes adapted to engagethe walls of said bore and said valve plate at one end and the other endcap at the opposite end and defining compression pockets within saidchamber for receiving compressible fluid from said inlet, said one endcap having a bypass port in communication with said chamber between saidinlet and said discharge on the compression side of said rotor, conduitmeans connecting said bypass port to said inlet, said valve plate havingan opening therethrough registrable with said bypass port, and means formoving said valve plate opening into and out of registration with saidbypass port in accordance with demand, whereby said valve plate can bemoved so that the opening therein is in full or partial registrationwith said bypass port to discharge Varying amounts of fluid from saidcompression pockets or said valve plate can be moved so that the openingtherein is out of registration with said bypass port to preventdischarge of fluid from said compression pockets.

6 2. The structure of claim 1 in which said means for moving said valveplate includes gear and pinion means driven by a motor means.

References Cited UNITED STATES PATENTS Re. 23,086 2/1949 Holl.

3,120,814 2/1964 Mueller. 3,135,460 6/1964 Galin 230*-138 3,295,7521/1967 Bellmer 230138 3,334,546 8/1967 Vuolle-Apiala 91-75 3,381,8915/1968 Bellmer 230138 FOREIGN PATENTS 420,501 12/1934 Great Britain.

DONLEY I. STOCKING, Primary Examiner.

WILBUR J. GOODLIN, Assistant Examiner.

